1. Field of the Invention
This invention relates generally to memory packages and more particularly to an improved dual reflection plate arrangement for a bubble memory package.
2. Prior Art
Bubble memory systems, which have become well known in the art, utilize a rotational magnetic field to effect the domain propagation necessary to the operation and function of the bubble memory device. It has been proposed, for example, to produce this rotational magnetic field for bubble devices using flat coils, one mounted on top of the other, with or without a reflection plate to provide the desired rotational field effect. A typical example of such a reflection coil package for bubble devices is found in the article entitled "Reflection Coil Packaging for Bubble Devices" by Masaki Takasu, Harumi Maegawa, Toshiaki Sukeda and Kazuo Yamagishi of the Fujitsu Laboratories Limited, Kawasaki, Japan which was published in the IEEE Trans. Magn., March 1975. The arrangement therein disclosed has the disadvantages that each of the two coils obstructs the flux of the other coil to some extent and the magnetic flux of one has to penetrate two winding layers of the other coil on its way into and out of the active bubble device area, thereby requiring increased coil current for compensation. Also, the electrical characteristics of the two coils are not identical, as indicated in the aforementioned article, because of the different physical displacements of the coils from the active bubble device area. Furthermore, in such systems cooling presents a problem, since all power dissipators, coils and chips are directly adjacent to each other without interspersed cooling elements. Yet another difficulty with such a system is that it does not lend itself to double level design unless the number of coils is doubled or the bubble chips are placed on both sides of the coil pair.